Puffer type gas blast circuit breaker

ABSTRACT

A puffer-type gas-blast circuit breaker comprises a pair of separable electrodes between which an arc is established and a nozzle having a throat of insulating material through which the arc extends. A plurality of injection passages extend radially of the nozzle into the throat region and intersect the throat at their inner ends. Pump means operates in response to circuitbreaker opening to inject arc-extinguishing gas through the injection passages into the throat, and this gas is forced to flow axially of the arc in opposite directions from the throat toward the spaced electrodes.

Unite States Patent [191 Noeske [11] 3,739,125 [4 June 12, 1973 1 PUFFER-TYPE GAS-BLAST CIRCUIT BREAKER [75] Inventor: Heinz 0. Noeske, Cherry Hill, NJ.

[73] Assignee: General Electric Company,

Philadelphia, Pa.

[22] Filed: Apr. 27, 1972 [21] Appl. No.: 248,123

[52] (1.8. CI. 200/148 A, 200/150 G [51] Int. Cl. H0lh 33/70 [58] Field of Search 200/148 A, 148 G,

[56] References Cited UNITED STATES PATENTS 3,150,245 9/1964 Leeds et al. 200/148 G 3,158,723 11/1964 Buechner 200/148 A FOREIGN PATENTS OR APPLICATIONS 951,409 3/1964 Great Britain ZOO/148 A Primary ExaminerRobert S. Macon Attorney-J. Wesley Haubner and William Freedman [57] ABSTRACT A puffer-type gas-blast circuit breaker comprises a pair of separable electrodes between which an arc is estab lished and a nozzle having a throat of insulating material through which the arc extends. A plurality ofinjection passages extend radially of the nozzle into the throat region and intersect the throat at their inner ends. Pump means operates in response to circuitbreaker opening to inject arc-extinguishing gas through the injection passages into the throat, and this gas is forced to flow axially of the arc in opposite directions from the throat toward the spaced electrodes.

11 Claims, 5 Drawing Figures l v j} PUFFER-TYPE GAS-BLAST CIRCUIT BREAKER BACKGROUND This invention relates to a gas-blast electric circuit breaker and, more particularly, relates to a circuit breaker of this type which relies upon a pump, or puffer, for forcing a flow of relatively cool gas into the arcing region to promote arc extinction. Prior patents of interest are: US. Pat. Nos. 2,297,8l8-Van Sickle; 3,150,245-Leeds et al; 3,291,948-Telford; 3,218,420- Forward; 3,406,269-Fischer; 3,588,407-Frink et al; and 3,602,670-Teijeiro.

In the type of circuit breaker that I am concerned with, circuit interruption is effected, first of all, by establishing an are between a pair of contacts or electrodes. The circuit breaker includes a nozzle of electrical insulating material having a throat of reduced crosssection through which the arc extends during circuit interruption. During the arcing period, a puffer operates in response to circuit-breaker opening to force a blast of arc-extinguishing gas into the arcing region.

In the usual puffer-type circuit breaker, the arc extinguishing gas enters the arcing region adjacent an upstream one of the elctrodes and, for th most part, flows axially of the are generally unidirectionally along substantially the entire length of the arc. A disadvantage of relying upon such unidirectional axial flow along the entire arc length is that the upstream electrode vaporization products developed during arcing are carried along the entire length of the arcing gap. Before the arcing gap can be cleared of such electrode vaporization products, it is necessary that such products first travel the length of the gap. This means that a relatively long time is required to clear the gap of such electrode vaporization products when arcing ceases at current zero, thus reducing the probability that the gap will be able to successfully withstand the recovery voltage transient that rapidly build up at current zero.

In one variation of the above-described prior design, some of the injected gas is allowed to exhaust through a passage in the upstream electrode; but a substantial, if not major, portion of the injected gas still flows axially of the arc unidirectionally along its entire length, thus carrying some of the electrode vaporization products into the arcing gap.

SUMMARY In my interrupter, I inject gas into the arcing region in such a manner that substantially none of the injected gas is required to flow axially of the arc unidirectionally along the entire arc length. This I accomplish by injection the acr-extinguishing gas via radially extending injection passages in the throat of the nozzle through which the arc extends and by exhausting in opposite axial directions from the injection region past the two electrodes. Thus, part of the injected gas flows from the nozzle throat past one electrode, and part flows from the nozzle throat past the other electrode. When the electrodes are in positions on opposite sides of the throat, substantially none of the injected gas is flowing unidirectionally along the entire arc length.

An object of my invention is to construct a puffertype circuit breaker in such a manner that the puffer is able to inject a gas blast that enters the arcing region at the nozzle throat and exhausts in opposite directions from the throat toward the electrodes.

In a preferred mode of operation, the arc in a puffertype circuit braker should clog the throat of the nozzle during high instantaneous currents, thereby blocking the flow of arc-extinguishing gas during this period. This prevents the pressurized gas from being wasted during high instantaneous currents, when it will have little or no effect on arc-extinction, and conserves the pressurized gas until it can be used more effectively, i.e., when the instantaneous current is approaching and has reached current zero.

Another object of my invention is to construct a puffer-type circuit breaker in such a manner that injection of the arc-extinguishing gas is blocked during high currents and is unblocked as the instantaneous current approaches zero to cause flow in the arcing region in opposite directions from the nozzle throat toward the spaced electrodes.

Another object is to provide a flow pattern that is exceptionally effective in clearing the nozzle flow passage of ablated nozzle material that has accumulated during periods of peak current and, more specifically, a flow pattern that acts to force ablated material at opposite sides of the throat to flow in axially-opposed directions away from the throat.

BRIEF DESCRIPTION OF DRAWINGS For a better understanding of the invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view, partly in section, showing a puffer-type interrupter embodying one form of my invention. I

FIG. 2 is an enlarged view of a portion of the interrupter shown in FIG. 1, with the interrupter depicted in its closed position.

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 2, with the contact structure omitted for simplicity.

FIG. 4 is a view of the interrupter shown in FIG. 2 except in its fully open position.

FIG. 5 is a sectional view of a portion of the interrupter of FIG. 3 showing the interrupter in an intermediate position through which its parts pass during an opening operation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring now to FIG. 1, there is shown a puffer-type gas-blast circuit breaker comprising an interrupter housing 10. Housing 10 comprises a cylindrical casing 12 of insulating material and a pair of end caps 14 and 16 suitably sealed to casing 12 at its opposite ends and acting as opposed electrical terminals for the circuit breaker.

The circuit breaker further comprises a pair of separable contacts, or electrodes, 20 and 21 located within the interrupter housing 10. Upper electrode 21 is a stationary electrode carried by a conductive contact rod 22 suitably joined to upper end cap 14. Lower electrode 20 is a movable contact carried by a movable conductive contact rod 24 that extends through lower end cap 16. A suitable guide 25 on lower end cap 16 guides contact rod 24 for vertical reciprocating motion. Flexible conductive braid 27 provides an electrical connection between movable contact rod 24 and lower end cap 16.

Located beneath lower end cap 16 is a housing portion 30 in which a horizontally disposed rotatable operating shaft 32 is journaled. This operating shaft is coupled to the movable contact rod 24 through a crank 34 keyed to shaft 32 and pivotally connected at its outer end to contact rod 24. Operating shaft 32 is suitably sealed where it extends through the walls of housing portion 30.

The entire housing is filled with a suitable arcextinguishing gas at a moderate pressure, e.g., sulphur hexafluoride at a pressure of about 50 psi. gage.

Referring now to FIG. 2, it will be seen that the stationary contact 21 comprises a conductive tube 40 that surrounds and is electrically connected to contact rod 22. This tube 40 is longitudinally slotted at its lower end to form circumferentially spaced contact fingers that are adapted to slide along the outer surface of movable contact during initial contact-opening movement and during final contact-closing movement.

Movable contact 20 is suitably joined to movable contact rod 24 at its upper end. Both members 20 and 24 are of a tubular construction to define an axiallyextending passage 46 therethrough through which gas can flow under conditions soon to be described. The gas flowing through passage 46 flows in a downward direction, exhausting therefrom via large exhaust openings 48 (FIG. 2).

Stationary contact 21 comprises a tubular contact member 45 disposed within the above-described conductive tube 40 and joined to stationary contact rod 22. Tubular contact member 45 at its lower end abuts movable contact member 20 when the circuit breaker is closed, as shown in FIG. 2. A passage 42 extends through the two tubular members 45 and 22 and has large exhaust openings 44 at its upper end (FIG. 1).

As will soon appear in greater detail, opening of the circuit breaker is effected by driving movable contact rod 24 in a downward direction from its position of FIG. 2 to that of FIG. 4, thereby separating movable contact 20 from stationary contact 21. Closing is effected by returning movable contact rod 4 upwardly from its postion of FIG. 4 to that of FIG. 2. Opening and closing forces are applied to movable contact rod 24 through the operating linkage 32, 34 of FIG. 1.

Surrounding contacts 20 and 21 is a nozzle 50 of electrical insulating material. Intermediate its ends nozzle 50 has a region 52, referred to herein as its throat, where the flow passage 54 through the nozzle is of its smallest cross-sectional area. Extending radially through the walls of nozzle 50 and intersecting throat 52 at their inner ends are a plurality of injection passages 56, through which arc-extinguishing gas can be injected into the throat region of the nozzle, as will soon be described.

Suitably coupled to the outer periphery of nozzle 50 is an annular piston 60 which can slide axially within the inner periphery of cylindrical casing 12. A suitable piston ring 62 in the outer periphery of piston 60 provides a seal thereabout that prevents pressurized gas from leaking past piston 60 when it is operating. The casing 12 acts as a cylinder within which piston 60 slides. Acting as an end wall of this cylinder is an annular member 64 suitably attached to casing 12 and extending radially inward therefrom. The inner periphery of annular member 64 slidably receives the outer periphery of nozzle 50 and acts as a guide for the nozzle during nozzle movement. A suitable seal 66 carried by annular member 64 prevents pressurized gas from leaking between the nozzle periphery and the annular member 64.

When nozzle 50 is moved downwardly from its position of FIG. 1, the gas present in space 67 between piston and end wall 64 is compressed and is forced from this space via injection passage 56 in the nozzle, as will soon be described.

Nozzle 50 is moved in a downward direction during a circuit-breaker-opening operation by force transmitted from movable contact rod 24 to the nozzle through a linkage 70. The linkage 70, which is schematically shown in the drawing, comprises two levers 72, each pivotally mounted on casing 12. Each lever 72 has a longitudinally-extending slot 74 in its outer end that slidably receives a transverse pin 75 in movable contact rod 24. A connecting rod 77 of insulating material connects each link 72 to the nozzle, being pivotally connected by a pin and slot connection 78, 79 to an intermediate point on link 72 and pivotally connected at its upper end to nozzle 50. At its lower end, connecting rod 77 is slidably received within a guide opening 82a in a stationary guide plate 82 of insulating material that guides the rod 77 for motion in a straight-line vertical path.

When contact rod 24 is moved downwardly during opening, it acts through pin 75 to force the two levers 72 to pivot in opposite angular directions from their position of FIG. 2 into that of FIG. 4, thus driving connecting rod 77 and the nozzzle 50 downwardly into their positions of FIG. 4. In the positions of FIGS. 2 and 4, each lever 72 is displaced from a horizontal reference plane 84 by angles 80 and 81 that are substantially equal. Each connecting rod 77 is effectively connected to its operating lever 72 at a point located approximately midway between the ends of the lever 72 when the circuit breaker is either fully-closed or fully-open. Thus, the distance traveled by nozzle 50 between FIGS. 2 and 4 is approximately half that traveled by movable contact rod 24 in moving between its fully closed and its fully open positions. The average velocity of the nozzle during such travel is therefore approximately half that of the movable contact.

By moving nozzle 50 at an average velocity approximately half that of the movable contact rod, I am able to maintain the throat 52 of the nozzle substantially midway between the ends of electrodes 20 and 21 during most of an opening operation. This contributes to generally symmetrically flow conditions in the nozzle, as will soon be explained.

When movable contact rod 24 is driven downwardly to open the breaker, it separates movable contact 20 from stationary contact 21 and withdraws movable contact 20 from its position of FIG. 2 within throat 52 of the nozzle, thereby drawing between the contacts an are that extends through the throat. This is best illustrated in FIG. 5, where the arc is shown at 55. Downward opening movement of contact rod 24 also acts through linkage 70 to drive nozzle 50 and piston 60 downwardly, thereby forcing arc extinguishing gas from cylinder space 67 through injection passages 56 into the arcing region. When arc-extinguishing gas is flowing through injection passages 56 it follows the flow 'paths illustrated by the arrows 83 in FIG. 5. That is, upon entering the arcing region in the throat 52, a portion of the arc-extinguishing gas flows axially of the arc toward one electrode 20, and the remaining portion flows axially of the arc toward the other electrode 21. During the initial portion of the opening operation, movable electrode is still within throat 52 of the nozzle and thus acts to block flow through the injection passages 56 into the throat region. This initial blocking is desirable because it allows piston movement which accompanies initial contact-opening motion to build up some pressure within cylinder space 67. Accordingly, when the opening operation has progressed to the point where electrode 20 leaves throat 52 to unblock injection passages 56, there is an appreciable pressure available in cylinder space 67 to force arc-extinguishing gas through the passages 56 into the arcing region.

If the instantaneous current is low, flow will take place through injection passages 56 into the arcing region. But if the instantaneous current is high, the pressure developed in the throat 52 by the arc will be so large that no flow can take place through the injection passages 56 into the throat. Under these high current conditions, the arc and the arcing products will, in effect, clog or block throat 52 and injection passages 56. This clogging under high instantaneous current conditions is desirable because it allows further downward motion of piston 60 to more effectively compress the gas in cylinder space 67 and, furthermore, prevents the gas in cylinder space 67 from being wastefully injected during the high instantaneous current period when it is of little or no help in extinguishing the are. But when the instantaneous current falls to a low value during the period just prior to and during current zero, the arc is no longer clogging the throat, and the high pressure built up during the earlier period of clogging is available to force an effective flow through injection passages 56. During this low current period, flow through passages 56 is highly effective in cooling the arc and the arcing products, thus promoting the desired rapid buildup of dielectric strength at current zero.

In prior puffer-type circuit breakers, it is typical for the arc-extinguishing blast to enter the arcing region in such a location that at least a portion of the blast flows axially of the arc generally unidirectionally along the entire length of the arc. This is disadvantageous because electrode vaporization products from the upstream electrode developed during arcing are carried along the entire length of the arcing gap. Before the arcing gap can be cleared of such electrode vaporization products, it is necessary that such products first travel the length of the gap. This means that a relatively long time is needed in such prior designs to clear the gap of such electrode vaporization products when areing ceases at current zero, thus reducing the probability that the gap will be able to successfully withstand the recovery voltage transient that builds up at current zero.

In my interrupter, substantially none of the arcextinguishing gas injected into the arcing region is required to flow axially of the arc unidirectionally along its entire length. By injecting the arc-extinguishing gas via the passages 56 in the throat of the nozzle 50 and by exhausting in opposite direcations from the injection region past the two electrodes 20 and 21, I force the electrode vaporization products to flow away from the highly stressed arcing gap rather than through it. This flow pattern is best illustrated in FIG. 5 where a portion of the arc-extinguishing gas entering through injection passages 56 flows from throat 52 toward electrode 21 and the remaining portion flows from throat 52 toward the other electrode 20. The arc-extinguishing gas reaching each electrode flows axially of the electrode both along its external surface and through the hollow passage extending therethrough, effectively carrying the electrode vaporization products away from the arcing gap. The flow that takes place through the hollow passages in the elctrodes is exhausted via discharge openings 44 and 48 in the respective contact rods.

The throat region 52 of the nozzle is of an electrical insulating material such as polytetrafluoroethylene (e.g., duPonts Teflon) which ablates when exposed to the high temperature of the arc These ablation products must be rapidly cleared from the gap as current zero is approached, and this function is served by the arc-extinguishing blast following the paths 83 of FIG. 5. This flow pattern of FIG. 5 is exceptionally effective in clearing the nozzle flow passage 54 of these ablation products for generally the same reaons as pointed out hereinabove with respect to the electrode vaporization products. That is, once the gap has acquired an appreciable length, substantially none of the ablation prod ucts are required to flow unidirectionally along the entire gap length. Generally speaking, the maximum distance required for these products to flow before leaving the gap is about one-half the gap length.

To assure a relatively high pressure in the nozzle throat region, this region should constitute the principal flow restriction for the arc-extinguishing gas being injected through passages 56. If the principal flow restriction was constituted by the passages 56, then sonic flow would occur in the passages 56 and supersonic flow in the throat 52, which would result in reduced pressure in the throat area. To preclude this condition from occurring, I make the effective cross-sectional area of the throat 52 smaller than the total effective cross-sectional area of the passages 56 in their regions of minimum cross-section.

It is undesirable to form a vortex in the throat region because the center of a vortex is a region of relatively low pressure, where an arc can burn with an undesirable degree of stability. To inhibit the formation of a vortex in my throat region, I rely upon circumferentially spaced radially extending passages 56 for introducing the arc-extinguishing gas, rather than relying upon a passage or space having an appreciable circumferential dimension. In this latter type of passage or space, the flow therethrough can develop an appreciable circumferential component of motion which encourages vortex formation upon entry into the throat. Another feature which inhibits vortex formation in my throat region is the enlarged mouth that is provided for each of the injection passages 56. This reduces the likelihood that diametrically opposed jets will be slightly misaligned in a manner which would cause the jets to flow past one another in opposite directions, thus contributing to vortex formation. With the enlarged mouths present, the jets are more diffuse, thus making them less likely to be so misaligned.

It is important that the main arc-extinguishing blast from the pump enter the arcing region at the throat 52 of the nozzle rather than at a location axially spaced from the throat. Entry at the throat promotes flow in opposite axial directions from the entry region to produce the flow pattern illustrated in FIG. 5. If the blast entered the nozzle passage at a location spaced from the throat 52, most of the gas would flow through the nozzle flow passage in a direction away from the throat,

assuming a vent at both ends of the nozzle. This would detract from the flow needed at the opposite electrode and in the throat to perform the desired cooling and scavenging function.

Another feature of my interrupter that contributes to a generally symmetrical flowpattern is that I move the nozzle during the interrupting process in such a manner that the throat 52 remains substantially midway between the ends of the electrodes, as was explained hereinabove. Thus, the flow impedance presented to axial flow by each of the two halves of the nozzle flow passage remains substantially equal during the interrupting operation, and substantially equal effective areas for exhaust are available at each end of the nozzle.

To make these exhaust areas more nearly equal so as to further promote a symmetrical flow pattern. I make the portion of the flow passage 54 through the upper half of the nozzle 50 slightly larger in cross-section than that portion through the lower half so as to compensate for the slightly larger diameter of the stationary contact 21 as compared to the diameter of movable contact 20. At any point in the opening operation following movement of contact 20 outside throat 52, the net crosssectional area of the flow passage 54 around the inner end of one electrode substantially equals that around the inner end of the other electrode.

When the arcing gap is very short at the beginning of an opening operation, the contacts, still being in the throat region, tend to block flow from the throat region through the nozzle flow passage. The axial passages extending through both contacts allow venting of the arcing products during this period, thus preventing an escessive accumulation of such arcing products that would intefere with dielectric recovery at a current zero.

When the arc has a high instantaneous current content and is clogging throat 52 and blocking flow through injection passages 56, some of the arcing products that are being generated, for example, by ablation of throat material, are forced radially outward through passages 56. For venting these arcing products to a lower pressure region, I provide bypass passages 86 of small cross section relative to injection passages 56. These bypass passages extend between the outer end of injection passages 56 and the nozzle flow passage, entering the latter passage at points spaced from the throat. Some of the arcing products can flow back into the nozzle flow passage through these bypass passages 86.

Another function served by the bypass passages 86 is to allow a small amount of arc-extinguishing flow from cylinder space 67 into the nozzle flow passage during high current periods when the arc is clogging the throat. Such flow promotes turbulence in the arcing region, which contributes to increased arc cooling.

It is to be understood that the bypass passages 86 are very small in cross section compared to the injection passages 56 and thus do not appreciably interfere with the desired pressure build-up in the cylinder space 67 during periods when the injection passages 56 are blocked by a high current are or by the movable contact 20.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects; and l, therefore, intend herein to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A puffer-type gas-blast circuit breaker comprising:

a. a pair of electrodes, spaced apart during an interrupting operation, between which an arc is established,

b. a nozzle primarily of electrical insulating material having a throat of electrical insulating material through which said arc extends during an interrupting operation,

0. a plurality of injection passages extending generally radially of said nozzle in the region of said throat and intersecting said throat at the inner ends of said injection passages,

d. pump means operable during a circuit-breaker opening operation for injecting arc-extingushing gas through said injection passages into said throat,

e. and means for forcing the gas injected into said throat to flow axially of said are in opposite direc tions from said throat toward said electrodes.

2. The gas blast circuit breaker of claim 1 in which when the arc is extending through said throat:

a. a portion of the gas injected into said throat flows from said throat toward one electrode, and

b. the remaining portion of the gas injected into said throat flows from said throat toward said other electrode.

3. The gas blast circuit breaker of claim 1 in which:

a. said electrodes are relatively movable in a circuitbreaker opening direction to elongate the are extending through said throat,

b. said pump means comprises a piston member and a cylinder member that are relatively movable to develop pressure for injecting said arcextinguishing gas through said injection passages,

0. one of said piston or cylinder members is coupled to said nozzle for movement therewith during at least a portion of the nozzles movement, and

d. coupling means is provided for causing said pump means to develop pressure for injecting said arcextinguishing gas through said injection passages in response to movement of one of said electrodes in a circuit-breaker opening operation.

4. The circuit breaker of claim 3 in which said coupling means causes said nozzle to move at a speed substantially less than the speed of said one electrode during circuit-breaker-opening movement of said one electrode, the direction of nozzle movement being such that said throat occupies a position intermediate and spaced from said electrodes during most of an opening operation.

5. The circuit breaker of claim 3 in which said coupling means causes said nozzle to move at an average speed approximately half the average speed of said one electrode during circuit-breaker opening movement of said one electrode.

6. The circuit breaker of claim 3 in which said coupling means causes said nozzle to move at such a speed that the nozzle throat remains approximately midway between the opposing ends of said electrodes during circuit-breaker opening movement of said one electrode following initial circuit-breaker-opening motion.

7. The circuit breaker of claim 1 in which:

a. said electrodes are relatively movable in a circuiteach of said mouths being substantially larger in crossbreaker opening direction to elongate the are exsectional area than its associated injection passage at tending through said throat, and points upstream of the injection passage from said b. said pump means comprises a piston member and mouth.

a cylinder member, both surrounding said nozzle, 10. The circuit breaker of claim 1 in which:

and relatively movable to develop pressure for ina. each of said injection passages extends into said jecting said arc-extinguishing gas through said inthroat from an upstream point located adjacent jection passages. said pump means,

8. The circuit breaker of claim 7 in combination with b. said nozzle contains bypass passages from some of means for coupling one of said piston or cylinder mem- 10 said injection passages extending from said upbers to a movable one of said electrodes to produce in stream point on the bypassed injection passage to response to at least a portion of the circuit-breaker locations in the nozzle flow passage spaced from opening movement of said one electrode relative movesaid throat. ment between said piston and cylinder members that 11. The circuit breaker of claim 1 in which: said develops pressure for said injection. throat has an effective cross-sectional area smaller than 9. The circuit breaker of claim 1 in which: at least the total effective cross-sectional area of said injection some of said injection passages have enlarged mouths passages. at their inner ends where they intersect said throat,

It is certified that error appears in tho .tzbove-idcntificd potent and that said Letters Patcnt are hereby corrected. as; shown below:

Column 8, line 47, change the period to a comma Column 8, after line '47, add as a new line e. said coupling means comprising means for coupling said one electrode to said nozzle.

Signed and sealed this 18th day of December 1973.

(SEAL) Attest:

EDWARD M.ELETCHER,JR. RENE D. TEGTMEYER Attesting Officer Acting Commissioner of Patents It is certified that error appears in the {above-identified potent and that said Letters; Patent are hereby corrected as; shown below:

Column 8, line 47, change the period to a comma Column 8, after line 47, add as a new line e. said coupling means comprising means for coupling said one electrode to said nozzle.

Signed and sealed this 18th day of December 1973.

(SEAL) Attest: I

EDWARD M.FLETCHER,JR. RENE D. TEGTMEYER Attesting Officer Acting Commissioner of Patents 

1. A puffer-type gas-blast circuit breaker comprising: a. a pair of electrodes, spaced apart during an interrupting operation, between which an arc is established, b. a nozzle primarily of electrical insulating material having a throat of electrical insulating material through which said arc extends during an interrupting operation, c. a plurality of injection passages extending generally radially of said nozzle in the region of said throat and intersecting said throat at the inner ends of said injection passages, d. pump means operable during a circuit-breaker opening operation for injecting arc-extingushing gas through said injection passages into said throat, e. and means for forcing the gas injected into said throat to flow axially of said arc in opposite directions from said throat toward said electrodes.
 2. The gas blast circuit breaker of claim 1 in which when the arc is extending through said throat: a. a portion of the gas injected into said throat flows from said throat toward one electrode, and b. the remaining portion of the gas injected into said throat flows from said throat toward said other electrode.
 3. The gas blast circuit breaker of claim 1 in which: a. said electrodes are relatively movable in a circuit-breaker opening direction to elongate the arc extending through said throat, b. said pump means comprises a piston member and a cylinder member that are relatively movable to develop pressure for injecting said arc-extinguishing gas through said injection passages, c. one of said piston or cylinder members is coupled to said nozzle for movement therewith during at least a portion of the nozzle''s movement, and d. coupling means is provided for causing said pump means to develop pressure for injecting said arc-extinguishing gas through said injection passages in response to movement of one of said electrodes in a circuit-breaker opening operation.
 4. The circuit breaker of claim 3 in which said coupling means causes said nozzle to move at a speed substantially less than the speed of said one electrode during circuit-breaker-opening movement of said one electrode, the direction of nozzle movement being such that said throat occupies a position intermediate and spaced from said electrodes during most of an opening operation.
 5. The circuit breaker of claim 3 in which said coupling means causes said nozzle to move at an average speed approximately half the average speed of said one electrode during circuit-breaker opening movement of said one electrode.
 6. The circuit breaker of claim 3 in which said coupling meanS causes said nozzle to move at such a speed that the nozzle throat remains approximately midway between the opposing ends of said electrodes during circuit-breaker opening movement of said one electrode following initial circuit-breaker-opening motion.
 7. The circuit breaker of claim 1 in which: a. said electrodes are relatively movable in a circuit-breaker opening direction to elongate the arc extending through said throat, and b. said pump means comprises a piston member and a cylinder member, both surrounding said nozzle, and relatively movable to develop pressure for injecting said arc-extinguishing gas through said injection passages.
 8. The circuit breaker of claim 7 in combination with means for coupling one of said piston or cylinder members to a movable one of said electrodes to produce in response to at least a portion of the circuit-breaker opening movement of said one electrode relative movement between said piston and cylinder members that develops pressure for said injection.
 9. The circuit breaker of claim 1 in which: at least some of said injection passages have enlarged mouths at their inner ends where they intersect said throat, each of said mouths being substantially larger in cross-sectional area than its associated injection passage at points upstream of the injection passage from said mouth.
 10. The circuit breaker of claim 1 in which: a. each of said injection passages extends into said throat from an upstream point located adjacent said pump means, b. said nozzle contains bypass passages from some of said injection passages extending from said upstream point on the bypassed injection passage to locations in the nozzle flow passage spaced from said throat.
 11. The circuit breaker of claim 1 in which: said throat has an effective cross-sectional area smaller than the total effective cross-sectional area of said injection passages. 